The two liquids to be emulsified are firstly automatically metered, mixed and then emulsified by causing the mixture to pass through a constant cross-section passage leading to a cylindrical plenum chamber, said chamber having a cross-section greater than the constant cross-section of the passage and such a length effective to be adjusted with side discharging, in order to obtain the desired emulsion.
As is known, the combustion of a liquid combustible, for example for heating, power producing and the like can be improved if said combustible is intimely emulsified with a certain amount of water having its particles, in the form of droplets, dispersed throughout the combustible liquid.
For example, the combustible oil and water are two immiscible liquids and, as they are emulsified, the liquid dispersed in droplets forms the so-called "dispersed phase", while the combustible liquid forms the so-called "continuous phase".
Before being emulsified, the two liquids are to be metered in the desired weight ratio, and this ratio must be maintained constant even if the required mixture (or combustible) amount changes depending on the heating the system has to produce.
With respect to the metering and mixing of the two immiscible liquids, these operation, as is known, can be carried out as follows:
(a) By using two vessels into which predetermined amounts of the two liquids are introduced and then poured in a single vessel thereby obtaining a rather homogeneous mixture.
(b) By introducing, through a cock, the desired proportion of the liquid to be dispersed: in this way, upon having set the upstream pressure, by operating the cock one can set the flow rate.
(c) By using a sophisticated and expensive method for making a gasoline-lubricating oil mixture, as used in some two-cycle motorcycle engine, which motorcycles are provided with two separate vessels, one for the lubricating oil and the other for the gasoline, respectively.
(d) By using a carburetor, as in conventional engines, to mix, according to the desired proportions, the gasoline and air; in this case, however, the mixing relates to a gas and a liquid and not two liquids.
(e) By using a nozzle, effective to spray the liquid to be dispersed into the continuous-phase liquid by the upstream pressure of this latter which pressure, if it is variable, is capable of varying the mixing ratio, or maintaining the ratio constant as the flow rate varies.
(f) By positive-displacement metering pumps (in general of the diaphragm type) effective to provide a variable flow rate, depending on the demand, for injecting the dispersed liquid.
With respect to formation of an emulsion of the two liquids, it is known to operate as follows:
(a) By using mechanical types of vibrators, effective to provide the strong mixing necessary to obtain the desired emulsion. This device comprises an ultrasonic cavitator agitating the mixture with a frequency of 20,000 Hz, thereby obtaining the dispersion.
(b) By using the so-called "impact effect" which occurs as the mixture particles, preliminarly brought to suitable speeds by exploiting a high pressure jump, (from 100 to 300 bars), are caused to impact against an obstacle.
(c) By using chemical additives (emulsifying agents) which as added to the mixture, and are effective to provide emulsifying chemical reactions.
(d) By causing at least one of said liquids to pass through a passive device located in the liquid flow-path. The liquid passes through a first tapering section, in which the pressure decreases under the Clausius-Clapeyron pressure for the liquid temperature, thereby generating bubbles. Then the liquid passes to a constant-cross-section element in which the bubbles are evolved. Due to this effect the bubbles shrink and abruptly expand, thereby providing the desired emulsion.
The known methods thereinabove described, however, are not completely satisfactory, mainly because of the great power to be expended for carrying out these methods and the complexity, high cost, and maintenance requirements associated with the apparatus.